Re: Suggested redline for mild 512
[Re: radar]
#2675141
07/07/19 11:33 AM
07/07/19 11:33 AM
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Joined: Jan 2003
Posts: 14,539 So. Burlington, Vt.
fast68plymouth
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On a chassis dyno with an auto trans, you can only get WOT readings as low as the whatever the converter stalls.
For example, If you had a converter that stalled 3500...... that’s as low of a rpm that you could apply full power to.
This can be one of the reasons a power curve on a chassis dyno might not look anything like the same motors power curve fron an engine dyno.
If you have 4500 stall, but the motor actually makes peak tq at 3800....... on the chassis dyno the peak tq would be at the beginning of the pull, at 4500.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Suggested redline for mild 512
[Re: AndyF]
#2675239
07/07/19 03:48 PM
07/07/19 03:48 PM
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Joined: Aug 2006
Posts: 2,141 junction city oregon
viperblue72
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junction city oregon
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That combo is probably all done by 6000 rpm. You can push it past that if you want, but I doubt the car will go any faster. Try it and see what happens. My guess is that you'll want to shift it at 5500 to 5800 with a rev limiter of 6100 or 6200. I agree!!!! Shift it at 5500-5800 and you could shift this thing anywhere from 5 to 6k and it won’t change your et much if any. I don’t think you’ll hurt anything shifting it higher but there won’t be any point. I had a 511 with 11.5 and mild ported heads with a 274@050 solid and even it was done @6k. The cylinder heads were just out of breath no matter the cam size. There’s very little point in stroking with a standard head. Other than it doesn’t cost much more. I did it because I plan to upgrade the heads and these were what I had for now. I moved these heads to a 440 stock stroke in a truck and with a 232@050 roller they are still done at 5500. Made 490hp@5200 and 554tq at 4000. It’s a nice flat curve and pulls hard. I think you’re making decent power for bolt on source heads. That would be enough for really low 11s in a. A-body.
Last edited by viperblue72; 07/07/19 03:51 PM.
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Re: Suggested redline for mild 512
[Re: BSB67]
#2675277
07/07/19 05:49 PM
07/07/19 05:49 PM
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Joined: Jan 2003
Posts: 14,539 So. Burlington, Vt.
fast68plymouth
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Interesting observation Russ...... I never did the math for 2nd gear.
I don’t know what the rear tire diameter is, but for 3.21’s, a 28” tire and 75mph I get 2889rpm in high gear with no converter slip. Multiply by the 2nd gear ratio of 1.45 and I get 4189rpm....... plus you’d add in some converter slip(which should be minimal with a “2400” converter).
I kinda took it that he was letting off the throttle at 5500, and that was the end of the pull...... but we don’t see the big drop off after the throttle is closed on the sheet...... so, maybe it’s not where the pull ended but where the data acquisition stopped.
I wanna say....... it’s a rare thing for me to be able to look at a chassis dyno sheet and think to myself....”yup...... that all looks right”.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Suggested redline for mild 512
[Re: BSB67]
#2675373
07/07/19 10:17 PM
07/07/19 10:17 PM
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Joined: Jul 2007
Posts: 1,688 Philadelphia
radar
OP
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OP
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Have you done the mph/tire dia/gear ratio math to determine rpm?
The reason the power is climbing at the claimed 5500 rpm is because I don't think 75 mph = 5500 rpm. I get something more like 4600 rpm. If I hadn’t heard him bounce off my limiters I would be asking the same question. The first time I was majorly freaked out because it sounded hreat then broke up a little and he let off. After making this post I had the same thought- looking at the sheet again. I had figured that the difference in 5000 and 5500 would be how wide 500 rpm was on the X axis. But no- that’s not time it’s mph so things happen faster on the right side of the paper. So all the dyno sheet tells me is that my torque curve was vastly increased by tuning the spark map. I also pulled up an internet gear, ratio axle ratio, & rpm to mph. Even if my 27.25ish tall tires grew to 28” the numbers don’t make sense unless the B&M converter is just mush and only spins the trans 75% of engine speed? Like I said it’s my first hotrod with two pedals.
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Re: Suggested redline for mild 512
[Re: radar]
#2675425
07/08/19 06:05 AM
07/08/19 06:05 AM
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Joined: Feb 2005
Posts: 4,333 Prospect, PA
BSB67
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Prospect, PA
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Have you done the mph/tire dia/gear ratio math to determine rpm?
The reason the power is climbing at the claimed 5500 rpm is because I don't think 75 mph = 5500 rpm. I get something more like 4600 rpm. If I hadn’t heard him bounce off my limiters I would be asking the same question. The first time I was majorly freaked out because it sounded hreat then broke up a little and he let off. After making this post I had the same thought- looking at the sheet again. I had figured that the difference in 5000 and 5500 would be how wide 500 rpm was on the X axis. But no- that’s not time it’s mph so things happen faster on the right side of the paper. So all the dyno sheet tells me is that my torque curve was vastly increased by tuning the spark map. I also pulled up an internet gear, ratio axle ratio, & rpm to mph. Even if my 27.25ish tall tires grew to 28” the numbers don’t make sense unless the B&M converter is just mush and only spins the trans 75% of engine speed? Like I said it’s my first hotrod with two pedals. Here is my conclusion, one or more of your data are simply wrong, and your power curve is not what you think it is when you think it is. If you tuned for improvement, fine. But you're on here asking about making sense of bad data. Your buddy needs to fix his stuff, or you need to go to a different dyno that is working properly. I will bet your peak power is below 5500, and best et shift rpm 6000 or less.
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Re: Suggested redline for mild 512
[Re: radar]
#2675461
07/08/19 10:16 AM
07/08/19 10:16 AM
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Joined: Jan 2003
Posts: 14,539 So. Burlington, Vt.
fast68plymouth
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There’s probably a shop with a dyno-jet 248 inertia dyno not too far from you. They’re the most popular chassis dyno from what I can see.
If you get more curious about how your build stacks up at some point in the future..... bring it to a shop that has one of those........ make sure the rpm pick-up is working properly....... do your pull in high gear....... make a few pulls.
There’s enough data out there taken with that type of dyno so you’d have plenty to compare to.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Suggested redline for mild 512
[Re: radar]
#2675502
07/08/19 12:14 PM
07/08/19 12:14 PM
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Joined: Aug 2003
Posts: 43,741 Bend,OR USA
Cab_Burge
I Win
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I Win
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Bend,OR USA
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I've found out not all motors and the rest of the parts in the car will want to be shifted at or near peak HP or peak torque to go as fast as the car can My first pump gas stroker motor was a 400 block stroked to 4.25 originally with a set of mildly ported 906 iron heads with 2.14 intakes and 1.81 exhaust valves and solid roller cam with 260@.050 on the intake lobes and 266@.050 on the exhaust ground on a 108 LSA installed 1 to 2 degrees advanced on the intake lobes. I put a Eddy low deck OEM style six pack intake and set of 440 vacuum carbs that I had C&J engineering modify for better street performance, that motor ended up having right at 9.25 to 1 compression ratio on all eight cylinders. I had that motor dyno tested and tuned the first time on a DTS engine dyno at the Carb shop facility in Ontario, CA, it made peak torque at 4500 RPM (644 Ft. Lbs.) and peak HP 612 at 5500 RPM. I ended swapping the heads later to a set of Eddy RPM that where CNC ported by MCH and I increase the stroke later to 4.300 to help up the compression to 10.29 to 1 . I had it dyno tested up here in Oregon on a Studka engine dyno that was not calibrated correctly at that time but it still made peak torque at 4500 to 4600 RPM and peak torque at 5500 an d5600 RPM depending on the tuning. I started racing the car by shifting at 5000 RPM and then 5500 and ended up learning that the car would run the quickest ET and MPH by shifting at or above 7000 RPM On your deal shift it where it wants to be shifted, it will talk to you
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Suggested redline for mild 512
[Re: AndyF]
#2675608
07/08/19 04:02 PM
07/08/19 04:02 PM
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Joined: Jan 2003
Posts: 16,936 NC
440Jim
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That combo is probably all done by 6000 rpm. You can push it past that if you want, but I doubt the car will go any faster. Try it and see what happens. My guess is that you'll want to shift it at 5500 to 5800 with a rev limiter of 6100 or 6200. I agree. with more detail than I was going to post.
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Re: Suggested redline for mild 512
[Re: 440Jim]
#2675628
07/08/19 04:59 PM
07/08/19 04:59 PM
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Joined: Jan 2003
Posts: 14,539 So. Burlington, Vt.
fast68plymouth
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Example of pretty much a picture perfect chassis dyno run.
Looks like probably a std trans, and the tq and hp scaling are the same, so the lines actually cross on the graph like you’d expect at 5252.
When the tq and hp are on different scales, but on the same graph, the lines won’t actually “cross” at 5252, but the values do.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Suggested redline for mild 512
[Re: radar]
#2675693
07/08/19 07:23 PM
07/08/19 07:23 PM
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Joined: Jan 2003
Posts: 14,539 So. Burlington, Vt.
fast68plymouth
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If you can get reasonably good and repeatable launches, and the ET/mph repeats pretty well....... and know what it weighs......... you’ll have a good idea what it makes for power.
Of course....... that assumes everything works as it “should”.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Suggested redline for mild 512
[Re: radar]
#2675705
07/08/19 08:01 PM
07/08/19 08:01 PM
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Joined: Jan 2003
Posts: 14,539 So. Burlington, Vt.
fast68plymouth
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Man it’s easy to twist some math around to make stuff sound good based on some rubbish! Truer words have never been spoken!!! I’d start out with a 5500rpm shift point, and after you have some decent consistency...... try upping it a couple hundred and see what happens. I’d be pretty surprised if your combo responded favorably to 6000rpm shifts....... but that’s why you test. What’s the basic engine combo again? Header size, carb, etc as well.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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